Steam quality indicator



Aug. 13, 1963 11.1. MORLEY STEAM QUALITY INDICATOR 8 Sheets-Sheet 1 Filed Feb. 25, 1959 INVENTOR THOMAS J. MOR LEY ATTORNEY Aug 13, 1963 T. J. MORLEY 3,100,395

STEAM QUALITY INDICATOR Filed Feb. 25, 1959 8 Sheets-Sheet 2 FIG. 2.

INVENTOR THOMAS J. MORLEY i A. zwfmfr ATTORNEY Aug. 13, 1963 T. J. MoRLr-:Y 3,100,395

STEAM QUALITY INDICATOR Filed Feb. 25, 1959 8 Sheets-Sheet 3 INVENTOR THOMAS J. MORL EY FIG 3 BY ,a 4. zwm? ATTORNEY Aug. 13, 1963 T. J. MORLEY 3,100,395

STEAM QUALITY INDICATOR Filed Feb. 25, 1959 8 Sheets-Sheet 4 INVENTOR THOMAS J. MOR LEY Gf A ATTORNEY Aug. 13, 1963 T. J. MORLEY 3,100,395

STEAM QUALITY INDICATOR Filed Feb. 25, 1959 8 Sheets-Sheet 5 FIG. 5.

PRESSURE IN .O08 .O12 .OIG .O20 .O24 SATURATED STEAM DENSITY gms/Cc FIG. 6.

|.OlO STEEL COUNTS PER MILLICURIE PER SECOND XIOOO INVENTOR THOMAS J. MORLEY o .l gm/emz oF WATE R 4, ATTORNEY Aug. 13, 1963 11.1. MORLEY STEAM QUALITY INDICATOR 8 Sheets-Sheet 7 Filed Feb. 25, 1959 1 52 fEsa FIG. 3A.

INVENTOR THOMAS J. MORLEY EKK /3 C 2mn-17M ATTORNEY Aug. 13, 1963 T. J. MORLEY 3,100,395

STEAM QUALITY INDICATOR Filed Feb. 25, 1959 8 Sheets-Sheet 8 Loge INTENSITY 04 U1 STRAIGHT LINE WATER 77 .oe .l2 .|e .2o .24 .2e .32 .56

P Grams/Cm2 FIG. 9.

LnIo SCALE FACTOR B Lg I ADD MULTIPLY BP AMP. OUTPUT- AMP, 1.5 V. /SUBTRACT /D'VDE *Log Io-Log! (|22 (|24 QuALlTY PRESSURE KlsTLER AMP.

PICK uP INVENTOR THOMAS J. MORLEY FIG. lO. BY

ATTORNEY United States Patent() 3,160,395 STEAM QUALITY {NDHATQR Thomas 5. Morley, 1271@ Turkey Branch Parkway,

Rockville, Md. Filed Feb. 25, 1959, Ser-.Nm 795,567 Y Y I 13 Claims. (Cl.` 73-192) (Granted under Title 35, US. Code (1952), sec. 266) The invention described hereinmay be manufactured and used by or for the Governmentof the United States of America for governmental.purposes Without the payment of any royalties thereon or therefor. l

Y This invention relates to steam. quality and condition indicators and more particularly to a device for measuring the moisture content of steam in a pipe when the moisture content is varying from zero to 50% kunder transient conditions where the full range of the variable occurs in two seconds.

In the case of -the steam catapult, the moisture content of the steam should be known and minimized in order to limit erosion by the entrained water, to provide for the etcient use of steam water, and to reduce pressure la-gs due to ow friction.

The steam quality indicator is designed to' measure the steam quality in a 6 or 12 inch diameter pipe Where the pressurevaries from 500 to 300 p.s.i.g., the moisture content varies #from 0 to 50%, the steam ilow rate is 0 to 7 00 lbs. per second, and the temperatures are the saturation values.

.In the past calorimeters such as the separating, throtthe followingfformula:

ltling, orsuperheating type havebeen used which involve i, 'collecting a representative steam sample andseparating and measuring the steam and Water." The majordifficulty seems to be. one of collecting 'a *representative sample under the varying ilow conditions during. a two' sfecond period. Furthermore if a multiplethrottling system were used where the steam lsamples .are thr'ottledginto ha, pluralityof expansion `chambers (say 20 overthe l second d period), the ,limited `moisturerange lof the' throttling measurementgof about 7% would require -a Asecondmoisture measurement suchA as that, given* aseparating` or super-heating calorimeter.` Y .y d x The primaryk object` of'thepresentginvention istol pro.-

` V,vide a syste'mvvhereby the densityofY the .stear'nfisontinously measured by means of'fast electrons `(betarays), the pressure of-'ftlie steam islmeasured,I and Athe 4steam quality is 'automatically calculated andjrecorded without any limitation `aslt 'conte'.'nnsteam iiovv rate. of.. Sampling problems :The Condities? Qf Suterheated steam its temperaturelcould be ,determined ,in vasimilarnianner."

vWet steam droplets.Y

l sjsteamlg'enerated ,with a" certairimportion "of entrainediiquid Water dispersedthereinY infminut'e measure the quantity density ofthe Water substance (liquid and vaporlby transversing a given volume of the material,

,Q2-aD"1 X 100 Where Dvl is the mean densityand a isa constant depending on geometrical considerations of the path. We

fWill,` as is usually done, assume that thermodynamic equilibrium exists with regard to temperature, pressure,

and equi-partition of energy. The quantity-M,` is then determined from a measurement of pressure and the v 3,100,395 Patented Aug. 13, 1963 rice WherefVg; isthe volume occupied'by the vapor andVl 1h@ Volume O'f'clped'by'he liquid. In the most unfavorable-conditionkof 50% moisture, the term h'a's'ia value of about 1.01 so that for our-purpose We may assu-me MI,=Mv Without introducing an error of more than one part in in the value of quality computed from Equation 1. yIt is of further interest to note FIG. 5 which is a plot of Ithe density of saturated steam as a function of pressure'. This is seen to be a lstraight line over the range of interest. It is in -fact a Very good straightl-ine through the origin, fand follows the form-ula Dvp=.00Zl6P, where Dvp 'is the idensity ofV saturated vapor at the absolute `pressureP.4 Over our ypressurey range this formula departs from Vthe tables by only 0.2%; We may therefore Write to a good (1.2% approximation A y j '.gQ- 002l'6P/Dv1 .'(4) 'where Dvynovv refers to the specicfvolume one cubic foot. f

y' A' betaray source andan in chamber are herein disbeta-ray'particleBeta-ray particles of a tixedenergy l.have a fairly Well deiined maximum range in anyl vmaterial because of thisv 'gradualY loss of energy. 'Beta-ray sources" emit a wholey spectrum of particleenergies up to a miximurn energy which the literature. l

VThe1absorptionbyfvvater-.oi radiation .fromvjstrontiuni- "sented inFI'. Iihe transmission isiplottedas'a. Afun-c!- tion ofgms/cmof Water, that isgyveight ofv-a'prisim of'vrater 1 ferri? inarea normal to' ythe radiation. `The reading wasLtakenthrough a'lO-mil steel.vvin'dow.y vfor Tea'sonslto beiapparent later. J It can lne-seen.'item1-an.v examination 'of this curve that'vvaterrsubstance absorbs lbeta radiation-.rather strongly andthat'v.0.251gm rof Water perv sq. 'reduce lthe. beta transmission by a factor d cfm; y. ,y Bet-a. raysvwill measure' only 'the .densityofelectrons in the material they traverse sov that a rbeta gauge installed ina steam 'line .will measure water density without regard *forjthe' state'of fthewater. Typicalbeta absorptions at ythe-,two lextremes of measurement may be computed. At

:500 p.=s.i;g. and r'100% quality the density of Water is 0.0458Y gm. per sq. cm. per inch thickness, so 'that six inches of this substance would reduce the beta-ray beam At 300 psig. lat 50% quality the beta-transmission reading in the rst case was 100 units .then :the reading in the latter oase is 51.3. A 6% decrease inadensity almost doubles the transmission. vIt is in- ,structiveto'consider for la moment that pressure remains constant at 300 p.s.i.g. and that quality Ivaries from 5,0 to 100 percent. 'Il-he density varies from 0.0513 per sq. cm. perr` inch to 10.0282. gm. per sq. cm. The trans.` mission reading changes from 51.3 to'263.' 'Thetran'sis theusual energy 4quoted in mission measurement varies by ve to one while the density varies 'two to one. It is apparent from these calf -theglf inchsteel Wal-ls, )Hence the betaray source and detectorrnust be inside the steam line.; The usugal sealed strontium sources caube {builtgwitha stainlesssteel-foil cover` andmounted inthe steam line, while the beta-rays y must 'be Vl-bronght'out'to thedetector Ithrough a thin wall.

Other objects and lfeatures'ofthe invention will hereinf afterbecomemore fully apparent' from 'the following description of :the annexed drawings, which illustrate a FIG; 3 is a cross-sectionryiew of the beta-ray source mounted on appe; c f

FIGJSA -is a detail view of the-source mount;

' FIG.; is' :tt-graph of the .deifyersiursted seam in gms/cc. as a functionof pressure;

'.FIG. 6 is a gnaphof the transmission of lstrontium- Yyttriurn 90L beta ,r-ays'through lan, -.0l.0 inch .Steel window and water;

Y AFlIG..-,7is'=a graph ofthe moisturer contentofga' [givenV Vvoluine of steam' versus thelogarithm'to thebase of theV intensity of the vIhefta*'radiation from a- =l0 milleurie i j vruthenium l/lrheniunr 1065" source `withyaryingeam g ion chamber 14 towards the backup plate 86. A cathode `in the lform of atube`102' is fastenedby angles 104 and FIG. 8 is4 a schematicgdiagra-mof the log IamplifierllS;

f. FIG.9' is a 'graphof the ion chamber v response Vto `strontium 90-beta-rays vtransmitted throughwater; and '1, i'FIG;` 10 ris ablock diagramof the analog computer :210. Referring now 'ltorthe drawinggwhereinlike reference I.characters klpsign'a-te` like: or corresponding Vparts through,-

' out thesevenal/ views, there is 'shown in FIG. lafppe 510 'the steam-iwhose'qualityfis to VAbe measured. tairayfsource'rn ismfunted at'one side ofthe pipe 7.5!. A lo "amplifier 18-connectede 4 Since the strontium chloride is soluble in water an .004 inch thick, stainless-steel seal 56 is placed in Contact with the strontium glass layer 48 and welded to the mount 40. A ring-shaped gasket 52 having a number of deformable serrations 53 -isV placed against the seal -50 and held in place by the outer seal disc 54 and housing 38. The inner surfaces oflthe disc 54 and housing 38 are beveled at 5'5 to provide an opening for the beta-rays from the layer 48 through the seal VSil `into the pipe 10.

Due to rthe high pressures in the stearn line (500 psig.) thel sealitl; Alayer 48' andwafer vv216 may'yield -but 1will notrupture because ofth'ebackingof the source mount 40. YThecornpletefunit-willbe subjected'to overpressure before Vactual use.1

`While the some 12Min normally be pressure tight,

a cap 56 is placed'o'ver fthe 'outerend of the source flange 28 and bolted thereto by. bolts 58 and nuts `60 to insure a' positive seal ,and ,to minimize accidental'lmovement of the rod-34 whichchanges the` calibration of the' indicator.

Referring to FIGS. Zand 4, an ion chamber assembly 70 is shown havinga flange 72 welded to pipe 10 diametrically opposite the beta raysource 12. A circular .llange'74 Yhas a number ofA circumferential holes 76 to ,allow bolts 78'and nuts 80 to clamp an ion chamber housing 82 between ii'ange 74 and ange 72. The ion chamber housing 82 has a central cylindrical section 84 which extends Vtoward the. Vpipeltl where its end `forms a backup plate 86 having a plurality of..l87 inch dia. holes 88. A betaray transparentwindow 16 made of a circular sheet of .007`5'ino'h thick stainless steel is lWelded to the pipe side of theback-up plate 86 and is further protected by a ring'90 welded at the outer circumference at 92 to window v,16 and'bacloup plateY 86. v A Micantarins'ulator 94 isfastenedby'screws 96 to the outer end "of the cylindricalV section 84 of housing 82 to by screw 100 .tn rinsrlator 94 and extendsthrough the bolts 10G-to, the insulator 94. Connecting leads 108 Y areIbrought"outV to spark plug type terminals 110V from .anodeQfSiand tube 102. v. Y'

f10rn`d emits'liigh'speed electrons toward an 4ion;,oliarnber I A v 50' Cir i 'nie imchamber -.14 issued, .with a @mure 'f 98% argon and 2% nitrogen at a pressure of 45` psi.

StrV ntiurn 90has a half lifewofh2t2 K years and therefore a change in the intensity of radiation of 6.3 %pei month is to beexpected. This small'change will allowarecalbrationfonceannonth by rneansof adjustngthe source f Aa `Bourfzllor'r.tube 'element vand isfa {type No. 145-72 series Maxwell and Moore,.lnc.'of Stratford, Conn... 'A Ilma/dds yolmeeted-.ronpressure amplier 2 4fwhose ou'- ,55

put isconnected-.fto another inputfto compwtrgm* "lf '-Theoutputofthe computer 20fis connected to osteam pressure!amplifie r 2h4 .is amplifier, rr'rtodelV KZX 2m Adev hy George A. Philbrick Researches Inc?, 4285 Columf bus Ave.,.Boston, Mass. I "i 'llhequali-ty recorderk 2 6 is'atype lZST yrrlnadef'by; the

Sanborn Co., Cambridge, Mass.A 60, g' alternate beta-ray source 12,;usng ruthenium 106,.

which hasga beta Yof 3.5 f"'nrev`.,'"instead of strontium 90 to the pipe to an inside threaded section 30 which is i. 'mounted' -a support plug 32. A source mount'rodV 34 is `threadedly engaged with support plug 3-2 softhart it may vlbe easily moved inland out and is xedv-inacalibrated posi- ',tionjby'nut 36. A'source housing 38 is threadedly ata 'jtached togrod 34 and holdssource'mount'll 4against* the .i y

ena 42 ef fodera. f Referring also to FIG. 3A, a recess y44-Vin the end of rnount lll supports a sinter'ed Aoxide wafer 46 (2.18 cmev.)l waslconsidered in the-case of a l2 inch pipe.

Fora l2 inch pipe ia source size ,of `l9l-n1illicuries was required atacost ofabout S2000-which 'was considered excessive.- Forao inchdi-stance between the source and ion chamber asource of only l0 millicuries w'as needed. This 6-inch distance on a'lZ inch pipe could be achieved kby moving the source mount ,rod 34 halfway across the rlp@-VV V .z Y .Y FIG. v7 depicts a family of pressure lines showing how ymoisture content variesfwith theflogarithim to' base of thebetaradiation.detected.` The standard deviation in log'e LisfOZ dueto nuclear statistics. I This will give, as villustratedin thediagranl, la standardV deviation ot y115% Where:

calibration.

Ruthenium has the advantage that it can be plated on the metallic source Window resulting in improved structural design over the strontium source which is laid downfas a glass. It has a disadvantage however, since it has a half life of one year so that corrections for decay must be made more frequently. It does emit about 30% gamma rays, 'which Will not affect thelgauge operation and will not pose -a shielding problem in the size contemplated.

y:From FIG. 7 Ithe function performed will be BP Q (m Ly-ln I) where Q is quality in percent, P is the pressure in p.s.i., 1 n10=the 4intensity of the radiation detected .through the steam at 100% quality (no entrained water), ln1 :natural logarithm 4of the radiation intensity Idetected through the steam and entrained water, yand B=a scale factor.. v

A schematic circuit of the log amplifier 18 is shown in FIG. 8 wherein the ion chamber .14 `has its an0de`93 connected to a plus voltage and its cathode y102 connected to the plate of diode V1 rand the grid `of triode V2. The output of tube V2 from its plate is connected to the input of almpliier 116 (a Philbrick KZX- model) having a gain A1 vand an output E3. The output of amplifier 116 is connected back to the cathode of V1 and to one end of R1. 'Ihe other end of R1 is connected to the input of amplifier 118 (similar to 1116) having 'an output En. Feedback resistor R2 is connected across amplier 118 from the other end -of R1 to En. f

The first tube element V1 is a vacuum diode operated with a negative cold-electrode potenti-al. The electron Yevaporation from the surface ofthe hot cathode follows the Maxwellian Yveloeity-distribution law land electron Y current'ows at negative potentials. The relation beq=electronic`change=1.59 10-19 coulombs,k *n k=Boltnmann constant'=1.372 10c-2a watt-sec./deg., 'Tr=absolutev,temperatuieof the hotcathode, K. '-ef=dio de plate-cathode potential and fis denotes the saturation cuiirent given'jby'the modified Richardsonfequation; fy y fs= sf1r2.expi -1q/k) p0) where S denotes surface area of hot cathode inom.2, is Ric'lla'rdsons Work functionand'is a constant. j

rIffthe lament current is xed, tthenis becomes acontion 6 becomes:

fier A1 and electrometer tube V2: suppose that the circuit is in a reference condition denoted by prime That is i=l; E2=E2 and E'2-Ecc=e'g. The currentthrough V2, that is Im becomes Ip for this state. For all conditions other than the Ireference condition, Ip dilTer-s from Ip by an increment, ip. Ip=1p+ip.

We may write down the general equation of the input voltage El to A1 as:

E1=EbbRr.(l'pl-p) The general equation for the output is:

Ea= (E11-Eng) Y stant =F, and'q/kT becomes a constant m. Then Equa- Proceeding to the amplifier stage represented by ampli- We have introduced BKK to accomplish two functions; first to provide the external bias c to the Philbrick KQX amplifier so that it will operate as a balanced amplifier and secondly to provide an arbitrary additive constant di related to log lo. Making use of the above relations, we can write: i

but ipRL=G2tE2-E2) where G2 is the gain of v2. So that:

The second amplifier stage A2 on FIG. 8 provides addi-y i impedance of (12) Where i is ion chamber cnr-rent,v ,u is the absorption coeicient for water substance, and D is the steam density. Equation l2 becomes:

` (log IO- logw (13) The output of the log Iamplifier E0: -D. Itis negative only for convenience in feeding into the input ofthe oomputeiz Combining Equations 8, 9 and 10 and noting that `e'=E;.,'-E2", we may write for Eg: r j Y l OHAFZ 17k-.Agca

Equation l4beoornes: s I

So that ,u is determined bythe setting oflRrZfw' *p if',

Equationlilbeeomemi A.

505 p.s.i.g. has a. density corresponding to lD5g5"= 0.2,75 Y Y gms/cm2; let 3655): 25, volt.Y Further, the density' of gms/cm?. This must produce a voltage E0(305`)": `,l5.4 volts. Let us `assume that ,we can initially calibrate an installation from steady stateY temperature and pressure` considerations, or alternately from the intnoduction of amplitier.

z.lutepressurel?l known absorbers between the beta source and the ion of these values is setaccurately at In; then theoretically,

at leastQonly two adjustments need be made to .set up the j'I'he proposed mechanism for determining steam quality 'presupposes lthat the output of the ion chamber varies in anexa'ct exponential manner as the density'of steam and j .water in the pipe changes. This is only approxi-mately however. The. departure for linearity is demonstrated IinV FIG. 9 in the curve for water. A straight line covering y the range 0.17 gms/cm.2 to 0.28 Vcm.2 has been drawn It satisfies the equation: Y

D= (9.92 10g l) /6.76

This is an enddpoint line and is not the ybest straight line. It is the type of working line however which would result in a routine two point calibration. The maximum departure from linearity is about 4% This is undesirable.

i' However, we may considerably reducethe deviation by usin'g'' type of compensatedion chamber. It is noted that the curvature of the experimental curve is concaver an amount of response current Alsimply by having a second small strontium sourcein the ion chamber assemblyf Since linearity will vary'with the actual fabrication and .set up of each assembly, the Yion chamber will be built-so that the effect of .the small source can'be adjusted tracted from: ln Io: YMultiplier L124 vnn'iltifplies scale factor Y '5 times thepi'essure/VPand-dividesthisquantity by the y il" output of subtractor 122 to obtain quality Q.

A listet thevsymbolsgarld'denitions as used inthe Y equations unless previously deiirI/a're vas follows:

@ Mv=mass of 'a'tervapor ina given volume. f.

' f M1='mass of' liquid water argiven volume. n xDv1=mean density offtherlwater (liquidandvaporl'in Y 4a.givenvolume i. 1 x Y '="a-constant epcndingonith geometry ofV a. given v l" `Vccvolume occupiedby the water'vapor for 1a Y'gi-ven'.VV volume. "itl Y p Vljivolume Y occupied by water fior a given volume. f .z 3... y fr Y f M,`= mass of 71.00% saturated'steam-which would ll agivenvolumefj- YPee-'abs lute ressure of-a'givenvolumeyfr I",-' the intensity ofthe radiaticmdetectedl through dry Y' Y 'stem i latusinaiisity ofthe'radiaaon detecten through ine k .steam whosemoisture is to be measured.

current vaiming through mode v1 or FIG. s.

- Y amplitierf-connectedfto thefoutputof. saiddolrchamber v for producingan output V.proportional Y toftheY diiference Y between Vthe logarithm of `the intensity Iof the. beta radiat1on.through dry steam and the logarithm of the intensity k of the betaradiation through the steam being measured; 45

Y ,a higher `intensity'beta source vto increase` the Vnumber of counts per second required for the statistical accuracy of .el-2%.V f i.'

It .shouldbe understood, of course, that the foregoing disclosure 'relatesto [only a preferred'embodiment of the vin ventimrjand that itis intendedto cover all changes and modifications of the example of. the invention. herein Y chosen for the purposesof the disclosure, which do not zero to 50% over a period oil seconds.

. forfma'xirnumlinearity-j Once adjustment is made. it 'Y willfremain fixed so -longras theinstrument".is used oyer .the same density-range. l v j .Y A block diagram'vof I llellalogcomputerfw is'shown` VIV*in FIG; V1.0 w-liere` in subtractor*:12 Zithe output in I is s ubconstitute. departures.: from; .the Y Spirit and. score of- 111e invention.'Y v

I claim:

yl. A steam condition indicator comprising radiation .transmitting means and'receiving means responsive to said radiationfor measuring the density of a given volumeof steam, pressure transducing means for measuring the pressure of said steam, and computing means connected to said pressure transducing means and to said receiving .means for calculating the steam quality.

2. A steam quality indicator according'toclaim 1 and `further characterized by said density measuring means comprising a 'beta-ray generator and an ion chamber having a thin steel window mounted on a perforated back-up Vplate for withstanding the 'high pressure steam.

3.v Asteam Vquality indicator 'according to claim 1 and 'further characterized .by a .recorder connected to; said computing means for vrecording the steam quality from 4.,AV steam quality indicator comprisingrneans for measuring the density of ;a given volume of steam in a Y pipe comprising abete-ray source mounted on one side Vo t -fsaid'pipev and Van ion chamber mountedon the other I side ofsaidpipe diametrically opposite saidj'beta ray fsourcehavingan outputproportional to theyintensityof said. beta-rays after passingthrough said steam; va log a pressure transducer :connected to. said pipe responsive i0" the Pressure Irl-Salo pipe :and Producing. anifoutput Y which is a function of ,the-pressure-irisaidpipe; an analog lcomputer. connectedrftot said. transdugl-` @gdm t9 Said :10g

i steam quality;

jamplier fordividing theyalue of the pressure-illg-'said '5o output proportionaltogsteamquality and a recorder conpipe iby the `output of said'log amplierntoproduce! an nected to the outputof Vsaid computer for recording the wherein said computing Ir'lea'nsr solves the-'equation marino here is thenqualityinpercent, P is ythe pressure'fin ps1., B 1s a scale factor-,flu lo is the natural logarithm of l.an electrical current proportional -to. t1he intensity of ra- Yof moisture contentof steam as a function of the natural logarithm ofthe, detected densityof the steam.

7. A condition vindicator for superheated steam com- Ypn'sng radiation transmitting means and receiving means responsive to said radiation formeasuring the density of a given volume of steam, pressure transducing means Afor measuring the Vpressure of said steam, and computing indlcatdr-laecording"ite.. claim 4 A means connected to said receiving means and to Said pressure transducing means for calculating the steam temperature.

8. Apparatus lfor determining the quality of confined steam comprising radiation means for producing radiation through said steam, receiving means for producing an output responsive to the intensity of radiation passing through said steam for providing a measure of the density, pressure-responsive transducer means for producing an output indicative of the steam pressure, and computer means coupled to said receiving means and to said pressure-responsive transducer means for calculating the steam quality from said outputs.

9. A steam quality indicator rior measuring the condition of a -volume of 'steam iiowing in a pipe comprising a beta ray source mounted ion one side of mhe pipe, an ion charnber mounted to detect :beta rays from said source transmitted through said pipe, ithe Ioutpnt off said ion chamber being proportional to the intensity of said beta rays, comparison means connected to said ion chamber for producing an output proportioned to the difference lbetween the logarithm ci the intensity of rthe beta nadiak ond aperture diametricaily opposite thereto, a support mounted in said housing and adjustable to positions of varying distance from said iirst aperture, a Wafer mounted on the side oft said suppont closest to said rst aperture and having a coating of beta ray producing material thereon, seal means mounted on said support fbet'ween said iirst aperture and said coating no prevent steam from reaching sa-id coating, lbeta ray receiving means mounted adjacent said second aperture tor producing an output proportional to the beta nay intensity, and comparison means for automatically comparing said output with an output corresponding to -a reference condition of steam.

11. Apparatus asdened in claim 10 Iand funther char iacterized lby said wafer comprising sintered valuminum oxide and said coating comprising strontium yttrium in chloride form fused in sodium silicate glass.

12. Apparatus as defined in claim 10,and fur-ther characterized iby said Ibeta ray producing material is Ruthenium, v

13. Apparatus as dened in claim 10 and rliurther characterized :by said beta ray receiving means comprising an ion chamber surrounding said second aperture, said chamber being lfilled a mixture lof argon and nitrogen and having a plunaiity of holes adjacent said aperture, an anode mounted centnailrly in said chamlber, a cathode in the ctiorm of a cylindrical section surrounding said anode in spaced relation thereto, and respective output leads for said anode and cathode, said leads being connected to said comparison means.

yReferences Cited in the ile of this patent UNITED STATES PATENTS 2,217,639 Luhrs Oct. 8, 1940 2,737,592 Ohmant Mar. 6, 1956 2,763,790 Olimar-t i Sept. 18, 1956 2,837,678 Hendee et a1. f. June 3, 1958 OTHER REFERENCES Handboek er Engineering Fundamentals, ey' o. W. Eslrbfach, volume I of Wiley Engineering Handbook Series, published in 1936 iby John Wiley & Sons, Inc., New

York (College Edition), pp. 7-33 and 740 relied on. 

1. A STEAM CONDITION INDICATOR COMPRISING RADIATION TRANSMITTING MEANS AND RECEIVING MEANS RESPONSIVE TO SAID RADIATION FOR MEASURING THE DENSITY OF A GIVEN VOLUME OF STEAM PRESSURE TRANSDUCING MEANS FOR MEASURING THE PRESSURE OF SAID STEAM, AND COMPUTING MEANS CONNECTED TO 